This is very tough to answer, because it depends on a lot of things we don't know.
If your server is experiencing performance issues, new hardware might help, or it might not. It really depends on what performance issues you are having and what is causing them. What you need to do now is to determine where your hardware bottlenecks are (CPU, memory, IO, etc.) and based on this infomation, make an educated choice what where your hardware needs to be boosted. You may also find that your performance problems are not hardware related, and because of this, new hardware won't help performance. Oftentimes, there are other issues, besides hardware, that negatively affect SQL Server performance.